Selenium-cell



(Na'ModeL) S. TAINTER. Selenium Cells.

Pa ten ted Dec. 14,1880.

C. &, musm/ N. PETERS. FHOTO-LITHOGRAF UNITED STATES SUMNER TAINTER, ()FWATERTOVVN, MASSACHUSETTS.

SELENlUM-CELL.

SPECIFICATION forming part of Letters Patent No. 235,590, dated December14:, 1880. Application filed September 25, 1880. (No model.)

To all whom it may concern:

Be it known that I, SUMNER TAINTER, of \Vatertowmcounty of Middlesex,and State of Massachusetts, haveiuvented an Improvement inSelenium-Cells, of which the following de scription, in connection withthe accompanying drawings, is a specification.

My invention relates to selenium-cells or instruments containingselenium as a portion of an electric circuit.

In an application of Alexander Graham Bell, filed August 28, 1880, anapparatus was shown and described for transmitting sound or producingvariations in electric current by the action of a beam of rays from thesun or other radiant bodies. The said apparatus contained an instrumenthaving selenium in an electric circuit, the resistance whereof is variedin ac eordance with variations in the active force of the rays fallingon the said selenium. In the said application various forms ofinstruments or cells containing selenium were described, some of whichwere not therein claimed, as they were not invented by the said Bell.One of the forms therein described,together with several modifications,forms the subject of the present application. In the said application ofBell it was stated that the selenium is of large resistance, and itshould consequently be interposed in the circuit in the form of aconductor of but slight length and of large area 5 and it may be furtherstated that it is desirable to arrange the selenium in circuit, so thatit will have as large a surface as possibe to be acted upon by the rays,the effect of which is greater at or near the surface upon which theyfall than upon the interior mass.

The instruments of the present invention consist, generically, of two ormore pieces of conducting material clamped or fastened together, but notin electric contact with one another, and so arranged that each sh allhave alarge number of points near, but not touching, the other, the saidpoints being mostly situated in or near a given surface intended to beexposed to the action of the rays. Selenium is fused in between the saidpoints, so as to electrically eonuect the two pieces of conductingmaterial, and as the said points are close together the seleniumconductor is very short, and as the points are very numerous theselenium is inl terposed in circuit in multiple are, or as acouductor oflarge area, and it affords, moreover, a large surface to be acted uponby the rays in proportion to the amount of the selenium in the circuit.In some instances the pieces ofconducting material are made as twoplates, one having a series of holes, and the other a series ofprojecting points or pins of slightly smaller diameter, to pass into thesaid holes, but not quite fill them, the annular spaces around the pinsbeing filled with selenium. The holes are made tapering, being smallest,and consequently approaching the pins more closely, at the surface to beacted upon by the rays, so that the selenium conductor is shortest atthe 1 surface, and consequently the electricity has the most direct paththrough the selenium where it is directly acted upon by the rays, andconsequently most sensitive. In another instance one of the pieces ofconducting material is shown as a netting, and the projections of theother piece pass into, but do not quite fill, the interstices thereof.In anotherinstauce several pieces of conductive material are formed asconcentric tubes, the external diameter of each being smaller than theinternal diameter of the nest larger, so as to leave concentric annularspaces between them. These spaces are filled near the ends of the tubeswith selenium, the whole forming a continuous surface to be 6X- posed tothe action of the rays.

Figure l is a top view, Fig. 2 an under-side view, and Fig. 3 is asectional view, of a selenium-cell constructed in accordance with myinvention; Figs. 4 and 5, plan and sectional views of a modificationthereof; Figs. 6 and 7, a plan and sectional view of anothermodification, in which a netting is used, and Figs. 8 and 9 a plan orsection of an instrument composed mainly of concentric tubes.

The instruments consist, essentially, oftwo portions, a I), ofconducting material, preferably brass, to be connected with oppositeterminals of an electric circuit.

Referring to Fig. 1, the portion a is a plate counterbored at c andprovided with a series of holes, d, made tapering, as shown in Fig.3,and of smallest diameter near the outer surface of the plate a, which isto be acted upon by the rays.

The portion 7) is a plate provided with a series of pins, 0, arranged topass into the middle of the holes (I when the two plates a b areproperly placed together, the pins 6 being smaller in diameter than theholes (I, so as to leave a series of annular spaces between the saidpins and the plate a surrounding them.

The two plates are properly matched together. A washenf, of insulatingmaterial, is placed between them to prevent electrical contact, and theyare tightly fastened together by screws 9 passing through the plate I)and insulated therefrom in any convenient manner, as by the washers hunder the heads thereof. A wire conductor forming one terminal of acircuit can be inserted under the head of one of the screws 9, and thusplaced in electrical connection with the plate (6. Abinding-screw, z, isemployed, to enable a wire to be readily connected with the plate I).

As thus far described the two plates a I) are insulated from oneanother, but have a series of points at d c in close proximity to oneanother, and lying in the outer surface of the plate a. The wholeinstrument is now heated to a temperature somewhat higher than themelting-point of selenium, which is rubbed over the surface of a plate,a, in the part perforated by the holes (I. The selenium will be melted,covering the surface of the plate a between the holes cl and the end ofthe pins 0, and filling the annular spaces between thepins e and theplate a, thus connecting the two plates to b in such manner that anelectric current can pass from one to the other through the annularrings of selenium 8. When solidified, on coolin g, the selenium is to betreated by a suitable process in order to acquire the properties ofconductivity and sensitiveness to the action of rays, which propertiesit does not possess when solidified from a liquid.

A process of treatment is fully described in ajoint application ofmyself and A. G. Bell, heretofore mentioned, to which referencemay behad.

It is sufficient to state here that the selenium should be heated asnearly as possible to its temperature of fusion without allowing it toactually melt, and then cooled, when it will be found to possess thedesired properties.

In the form illustrated in Figs. 4 and 5 the portion 1) is formed as abox, having a flange or-side, b, with an internal shoulder, 2.

The plate a, provided with tapering holes (I, is secured by screws 3 toa plate, a, of glass or other suitable insulating material, fitted toenter the upper portion of the flange b and rest on the shoulder 2thereof, where it is held connected with the plate I) by the screw g.The plate a is slightly smaller than the internal diameter of the flangeb, and the shank of the screw 9 passes through without touching theplate a, which is thus insulated from the plate I), the latter beingprovided with pins 6 to,pass into the holes d, as in the instrumentpreviously described. In thisinstance the selenium to connect the twoplates to b may be placed, in a pulverized condition, in the holes d, itthen resting on the plate a, inverted for that purpose, and after thetwo portions a b have been properly fastened together by the screw 9 theselenium will be melted and treated or annealed, as in the otherinstance.

In Figs. 6 and 7 the portion a is shown as a network of interwovenwires, the meshes or interstices of which correspond in function to theholes (I of the plates a, hereinbefore described.

The plate I) is provided with a series of intersecting groovescorresponding in position to the wires of the netting a, and leavingbetween them a series of square projections, 0, corresponding infunction to the pins 6 of the other forms, they being slightly smallerthan the netting a, which may rest on pieces of insulating material f,and thus be electrically separated from the portion 1).

When selenium is fused over the upper surface it completes the electriccircuit between the portions to b, as before described.

In the form shown in Figs. 8 and 9 the portions a b consist of a seriesof concentric tubes separated from one another by a slight space andprovided with flanges m, to enable them to be properly secured together.Annular washers f are placed between the said flanges m, and tubularpieces of insulating material are placed between the concentric tubes,but do not extend quite to the ends of the said tubes. A series ofconcentric annular channels are thus formed between the said tubes, andthese channels are filled with selenium, properly prepared, as beforedescribed, which thus forms an electric connection between the saidtubes. The alternate ones, a, of the said conducting -tubes areelectrically connected with one terminal of an electric circuit, and theintermediate ones, I), electrically connected with the other terminal.

The insulating material employed should be of a kind not injured by theheat necessary for treating the selenium. Mica is a suitable materialfor this purpose, in most instances, and has generally been used by meinthe construction of these instruments.

The construction shown in Figs. 1, 2, 3 is very simple, and theinstrument is readily taken apart, if desired, the selenium in that casebeing melted.

It has been stated that the selenium, when fused upon the surface of theinstrument, covers the conductive material.

I have obtained the best results by removing, by filing or otherwise,the superfluous selenium, leaving as an exposed surface only that lyingbetween the different portions of the conductive material.

By making the holes d tapering, as shown in Figs. 3 and 5, the parts ofthe conductives a b which are in closest proximity, and consequentlywhere the selenium conductor is shortest, lie on the surface to beexposed to the rays.

It is obvious that various modifications of the above-described formsmay be employed,

l l l theessential features of the invention being the two portions ofconductive material electrically insulated from one another, except at aseries of points where they approach one another closely, and where theyare connected by selenium or other equivalent material havin g thedesired properties of sensitivcness as to their electrical conductivityto the action of rays falling upon it, the said connecting materialbeing a conductor of short length and large area, and having a surfacelarge in proportion to its total amount, in proper position to be actedupon by the rays.

I claim- 1. In an instrument containing selenium as a portion of anelectric circuit, two pieces of conducting material insulated from oneanother and provided with a series of points near, but not in contactwith, one another. and selenium placed between the said portions ofconducting material at the said points to electrically connect them,substantially as described.

2. In an instrument to interpose selenium in an electric circuit, twoplates of conductive material rigidly held in relation to one anotherwithout electrical contact, one plate being perforated with a series ofholes or openings, and the other provided with a series of projectionsto pass into, but not fill, the said openings, and selenium interposedbetween the said projections and the perforated plate, substantially asdescribed.

3. Two conductive plates, one provided with a series of openings and theother with a series of corresponding projections, and seleniuminterposed between the plates in the said openings to form, with theplates, a continuous surface, the plates being properly shaped toapproach one another most closely on the said surface, as and for thepurpose described.

4. The herein-described selenium-cell, consisting of two plates and aninterposed layer of insulating material fastened rigidly together, oneplate being provided with a series of tapering holes and the other witha series of projecting pins passing into the said holes, and selenium tocomplete the electric circuit between the two plates, substantially asdescribed.

In testimony whereof I have signed my name to this specification in thepresence or" two subscribing witnesses.

SUMNER TAINTER.

Witnesses:

PHILIP MAURO, BARTRAM ZEVELY.

